drm/sun4i: Use lists to track registered display backends and TCONs

To support multiple display pipelines, we need to keep track of the
multiple display backends and TCONs registered with the driver.

Switch to lists to track registered components. Components are only
appended to their respective lists if the bind process was successful.
The TCON bind function now defers if a backend was not registered.

Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>

drivers/gpu/drm/sun4i/sun4i_tcon.c

@@ -25,6 +25,7 @@
 #include <linux/regmap.h>
 #include <linux/reset.h>
 
+#include "sun4i_backend.h"
 #include "sun4i_crtc.h"
 #include "sun4i_dotclock.h"
 #include "sun4i_drv.h"
@@ -407,14 +408,18 @@ static int sun4i_tcon_bind(struct device *dev, struct device *master,
 {
 	struct drm_device *drm = data;
 	struct sun4i_drv *drv = drm->dev_private;
+	struct sun4i_backend *backend;
 	struct sun4i_tcon *tcon;
 	int ret;
 
+	/* Wait for a backend to be registered */
+	if (list_empty(&drv->backend_list))
+		return -EPROBE_DEFER;
+
 	tcon = devm_kzalloc(dev, sizeof(*tcon), GFP_KERNEL);
 	if (!tcon)
 		return -ENOMEM;
 	dev_set_drvdata(dev, tcon);
-	drv->tcon = tcon;
 	tcon->drm = drm;
 	tcon->dev = dev;
 	tcon->quirks = of_device_get_match_data(dev);
@@ -459,7 +464,9 @@ static int sun4i_tcon_bind(struct device *dev, struct device *master,
 		goto err_free_dotclock;
 	}
 
-	tcon->crtc = sun4i_crtc_init(drm, drv->backend, tcon);
+	backend = list_first_entry(&drv->backend_list,
+				   struct sun4i_backend, list);
+	tcon->crtc = sun4i_crtc_init(drm, backend, tcon);
 	if (IS_ERR(tcon->crtc)) {
 		dev_err(dev, "Couldn't create our CRTC\n");
 		ret = PTR_ERR(tcon->crtc);
@@ -470,6 +477,8 @@ static int sun4i_tcon_bind(struct device *dev, struct device *master,
 	if (ret < 0)
 		goto err_free_clocks;
 
+	list_add_tail(&tcon->list, &drv->tcon_list);
+
 	return 0;
 
 err_free_dotclock:
@@ -486,6 +495,7 @@ static void sun4i_tcon_unbind(struct device *dev, struct device *master,
 {
 	struct sun4i_tcon *tcon = dev_get_drvdata(dev);
 
+	list_del(&tcon->list);
 	sun4i_dclk_free(tcon);
 	sun4i_tcon_free_clocks(tcon);
 }